Former Vice President Al Gore won’t be endorsing Hillary Clinton. Or speaking at the Democratic National Convention (DNC). Could it be his long, complex history with the former first lady? Or that he secretly favored climate change champion Bernie Sanders? Maybe it’s the treasure trove of emails posted over the weekend on WikiLeaksshowing how the DNC colluded with the Clinton campaign and Democratic-leaning news organizations to deprive Sanders the nomination.

Either way, Gore’s self-provoked expatriation from the Democratic party is just one more indication of an convention in chaos. Some have speculated Gore is too busy focusing on climate change, and can’t take the time for a video address √† la Marco Rubio at the RNC.

The Protesters were Chanting “Hell No, DNC, we won’t vote for Hillary” and “This is what democracy looks like,” https://t.co/2pCgCn3wtC

Gore won’t endorse Hillary.

Unlike past elections, this time Gore has refused to formally endorse the presidential candidate Hillary Clinton, and is one of the most conspicuous holdouts not joining the Clinton coronation. But if anyone knows Hillary at her best (and worst), it’s Al Gore, who spent eight years in the White House working with her and President Bill Clinton. Sources also say he has a “complicated” relationship with the nominee. Gore has also maintained an eerie silence since Clinton officially became the nominee, something rare for a party that demands unity above all else. But people familiar with Gore know he thinks climate change comes first and everything else is secondary.

In May, CNN made a ruckus when Mitt Romney and a few prominent Republican establishment figures decided not to attend the Republican convention. Alex Burns of the NY Times even tweeted:

Imagine if Bill Clinton, Al Gore, John Kerry and Ted Kennedy all declined to show up at the 2008 Dem convention. That’s Cleveland 2016.